As only one trap can exist on any one square, if you cannot manually #untrap a physical trap, you can remove them by entering the square and digging a pit, replacing the original trap with a pit trap. You can then leave the pit and avoid it, or it can be filled in by pushing a boulder in to the pit to remove the pit. The down side to this strategy is that you must expose yourself to the trap to attempt to remove it.

Some trap types can only be generated below a certain dungeon depth in case of ordinary rooms-and-corridor levels.[1] Maze levels are handled differently,[2] and special levels and quest/mines fillers get a third type of trap distribution.[3]

Many traps affect monsters, including pets, differently than they affect you. Some traps cannot even be triggered by monsters.

^ Anti-magic field

This trap will drain between 2 and your experience level + 1 points of your spell power.
If this would cause your spell power to go below zero, your maximum spell power will be permanently reduced by that amount, and your spell power becomes zero.[4] Anti-magic fields have no effect on your maximum spell power if it is zero.

If you have magic resistance, you take damage instead of losing power. The damage is at least d4, with an additional d4 each if you:

^ Arrow trap

These fire arrows at you or whoever else steps on them, which generally do 1d6 damage.

These traps can be a useful source of arrows. While standing on or adjacent to the square with the trap, try using the #untrap command. You might fail a few times as a few more arrows hit you, but if you are lucky, you will obtain a large supply of arrows (50 - rnl(50)[6].) Each time you or a monster triggers this trap there is a 1/15 chance that it will disappear. Any arrow that hits you or a monster is guaranteed to be lost. The average number of arrows you obtain by disarming is dependent on luck, but is higher than the average number you obtain by stepping on the trap until it disappears.

Generation: May be randomly generated at any dungeon level.

To remove: #untrap, or trigger it repeatedly until it runs out of arrows ("You hear a loud click!")

^ Bear trap

A bear trap renders you immobile for several turns. During this time, you can attack and be attacked, but you cannot move from the spot. When caught in a bear trap, you are unable to kick. For some reason, escaping a bear trap is 5 times more likely when moving diagonally than when moving orthogonally.[8] Monsters can be trapped too.

It is possible to #untrap a bear trap. If successful, it will appear as a beartrap on the dungeon floor. You may then pick it up and apply it to a new location. If unsuccessful, you will become trapped. If a bugbear or an owlbear gets stuck in a bear trap outside your sight, then you will hear "the roaring of an angry bear". If you are caught in a beartrap, you can not untrap yourself.

^ Dart trap

Similar to an arrow trap, but with darts. Darts will generally do 1d3 damage. Darts can be poisoned (1 in 6 chance), so be careful.

Disarming a dart trap will recover a large stack of darts, but this should probably not be attempted by characters lacking poison resistance. Like arrow traps, dart traps have a 1/15 chance of disappearing each time they are triggered; darts that hit always disappear; and you will obtain more darts by disarming than by triggering it (on average (50 - rnl(50) darts).[10])

Generation: May be randomly generated at any dungeon level.

To remove: #untrap, or trigger it repeatedly until it runs out of darts ("You hear a soft click.")

^ Fire trap

This will set off a column of flame underneath you. If you lack fire resistance, you take 2d4 damage, and lose maximum HP equal to between zero and the damage you took. If you are fire-resistant, you lose d2-1 HP (i.e. one point or none), and no maximum HP. The trap will attempt to burn some article of clothing with an equal chance of each of 5 types (helmet, torso, shield, gloves, or boots) being selected. If the selected armor is not torso, but is either burnproof, thoroughly burnt, or not worn, a different type of armor will be selected. If blessed, the chance of the selected armor burning is subject to luck consideration. If the final armor selection is not body armor (regardless of whether the armor survived the luck roll), there is a 1/3 chance that scrolls, potions, and spellbooks in the main inventory will not be subject to burning. Otherwise all scrolls, potions, and spellbooks will have a 1/3 chance of burning.

Generation: Fire traps are only randomly generated in Gehennom, maze levels (including to the left and right of the Castle), the Plane of Fire, and some quests, notably the Valkyrie quest. In Gehennom, fire trap generation is increased. 1/5th (20%) of all randomly generated traps in Gehennom are guaranteed to be fire traps.

A magic trap or trapped box or chest has a chance of acting as a fire trap even where a fire trap cannot be generated. A magic trap always acts as a fire trap if activated by a monster.

If a fire trap is created on top of ice (which is common in the Valkyrie quest), stepping on it will melt the ice and replace it with a pool of water, potentially resulting in drowning.

To remove:Dig a pit into the ground while standing on the trap, then fill the pit. In SLASH'EM, it is also possible to disarm a fire trap with a non-cursed potion of water, similar to using a potion of oil on a squeaky board. This will also generate 1-4 potions of oil based on luck. Since oil can then be diluted back to water, the large number of fire traps in Gehennom offer an effective way of multiplying one's water potions.

^ Hole

Holes simply drop you down a number of levels. 2-3 levels is a typical fall distance, but there is no upper limit, bar extreme improbability, on how many levels it is possible to fall through, although you won't fall beyond the Castle. Monsters never fall more than one floor.[13]

One technique for dealing with this problem is to go down any stairs you encounter and then go back up again immediately. This way, if you should ever fall down to that level you will know where the exit is. A high dexterity stat will reduce your chances of falling down the hole should you accidentally step on it.

The same hole is not guaranteed to lead to the same location, or even the same level, even if an object, monster or pet went through it immediately before you.

Generation: Hole traps are much less likely to be randomly generated than other eligible types. Only 1 in 7 attempts to randomly place a hole trap will succeed. Hole traps cannot be randomly generated on levels with non-diggable floors such as the Vibrating square level or the Castle. If the floor is non-diggable, the hole trap is replaced with a falling rock trap. Cannot be generated beneath a boulder. Unlike other traps, holes are always generated visible.

^ Magic trap

Monsters will fail to trigger this trap with 20/21 chance, in which case the trap will do nothing and not be revealed to you. If the a monster triggers the trap it will generate a pillar of flame, acting like a fire trap.

^ Falling rock trap

This triggers a falling rock, which hits you on the head for 2d6 damage, unless you are wearing some kind of hard hat, in which case the damage is reduced to 2. The rock stays on the ground, so it is possible to use them as a rock source, although the trap will be exhausted eventually (1/15 chance each time it is triggered).

Early pet deaths are often due to this type of trap, earning it the nickname of "Puppy Pounder" or "Kitty Killer".

^ Land mine

Land mines are hidden explosives, especially common in the Fort Ludios. When triggered, they wound your legs and are replaced by a pit in which you fall after the explosion. You may #untrap a land mine from an adjacent square, and then pick it up and install it elsewhere, just like with a bear trap.

Monsters will fail to trigger this trap with 2/3 chance, the rest of the time it affects them just as it does you.

Generation: Never randomly generated above dungeon level 6; the main treasure vault in Fort Ludios is often full of them.

To remove: #untrap, or just set it off (although the latter will replace it with a pit).

^ Level teleporter

This teleports you to a random location on a random level. If you have teleport control and are not stunned, fainted, frozen, 1/5 chance if confused, then you can specify the level you (and adjacent/leashed pets) will go to. Otherwise, you or monsters activating the trap will be teleported up at most to level one, down at most three levels, but never down out of the main dungeon, or into the Sanctum before the invocation ritual. In the Endgame, you, monsters with the Amulet, and elementals on their plane cannot level teleport at all. All eligible target levels are equally likely.[18]

After a (un)successful teleport of the player, it vanishes. You may remain on the same level and receive the message "You shudder for a moment."

Magic resistance will prevent you, but not monsters, from being teleported ("You feel a wrenching sensation."). Under certain conditions, you can use a normal teleport trap, even if you have magic resistance (for more details, see Teleportation trap). However, you cannot do the same with a level teleporter.

^ Pit

Pits in the ground open up when you walk over them, causing 1-6 damage. This will also abusestrength and dexterity. They require 3-7 turns to "climb to the edge" and escape. You may #jump out of a pit or (a)pply a whip to escape. While in the pit, any light source you are carrying will not travel beyond the walls of the pit. Falling into a pit as a pit fiend or a pit viper will generate YAFM.

Generation: May be randomly generated at any dungeon level. Cannot be generated beneath a boulder.

^ Polymorph trap

A polymorph trap turns you into another monster for a limited time. Monsters can make use of them, too. However, monsters (including pets) that are polymorphed stay in that form permanently. After a successful polymorph of the player, it vanishes.

Encyclopedia entry

Portals can be Mirrors, Pictures, Standing Stones, Stone
Circles, Windows, and special gates set up for the purpose.
You will travel through them both to distant parts of the
continent and to and from our own world. The precise manner
of their working is a Management secret.

[ The Tough Guide to Fantasyland, by Diana Wynne Jones ]

^ Rolling boulder trap

This is a trap in two parts. The actual trap is a switch, which, when activated by stepping on it, sets a nearby boulder rolling towards you. The existence of these traps can sometimes be inferred by an incongruously placed boulder in a room. The path between the boulder and the trap must be clear[23], though the boulder will pass through some dungeon features like fountains. When it hits another boulder, "you hear a loud crash as a boulder sets another in motion", it stops, and the other boulder begins moving.

Generation: Never randomly generated above dungeon level 2.

To remove: Destroy the boulder, move it beside the trap, or move it out of line with the trap, then activate the trap; a boulder trap only activates if there exists a boulder on one of the two designated launch squares, and activating the trap when there is no suitable boulder will destroy it.[24][25]

In UnNetHack, there is a 1/10 chance that the rolling boulder trap will have an archaeologist corpse, a bullwhip, and a 1/3 chance of a fedora.

^ Rust trap

This trap will spray you with water, rusting any rustable items you wear where it hits. Wielded iron objects or scrolls are also affected, but not spellbooks or potions. Gremlins like to use these traps to multiply. Iron golems will be instantly destroyed by these traps. If you are polymorphed into an iron golem then you will take damage equal to your monster form's maximum hp, killing your monster form and reverting you to your natural form. The half physical damage extrinsic applies.

Generation: May be randomly generated at any dungeon level.

To remove:Dig a pit into the ground while standing on the trap, then fill the pit. In SLASH'EM, #untrapping a rust trap will, if successful, turn the trap into a fountain.

^ Spiked pit

These are just pits which do 1-10 damage. The spikes are sometimes (1 in 6 chance) poisoned, which can be fatal for a character without poison resistance. Note that the chance of spikes being poisoned is re-randomized every time you fall on them, not per spiked pit. Metallivores can eat the spikes out of a spiked pit, turning it into a normal pit. The spikes are never poisoned when a monster falls in.[29]

WARNING: Pets that fall into a pit can be helped out by standing adjacent to the pit and untrapping in the direction of the pit. When you do this with a spiked pit, if you fail to remove your pet, they will suffer the effects of falling onto spikes each time you fail, making them angry (reducing their tameness) and counting as abuse for resurrection from the wand of undead turning. If they die at your hands, you suffer the consequences of killing them in a trap yourself (-15 alignment and an angry god).

^ Squeaky board

A squeaky board wakes nearby sleeping monsters. If a monster steps on a squeaky board on your level, you "hear a distant <note> squeak", or "A board beneath <monster> squeaks <note> loudly" if in sight. (The frequency of the squeak is meaningless, but each trap has only one note associated with it.) For you, "nearby" means that the square of the distance between you and a monster is less than 20 times your level (level 5 gives a 10 square radius, level 10 a 14, level 15 a 17). For monsters "nearby" means that the square of the distance is less than 40 (a 6 square radius).[31]

The note may be any note of the chromatic scale[32], and no two boards on the same level will squeak with the same note, unless there are at least 13 squeaky boards on the level[33].

Generation: May be randomly generated at any dungeon level.

To remove: #untrap, but you must select a potion of oil (which will be consumed) or a charged can of grease (one charge will be consumed).

Encyclopedia entry

A floorboard creaked. Galder had spent many hours tuning them,
always a wise precaution with an ambitious assistant who walked
like a cat.
D flat. That meant he was just to the right of the door.
"Ah, Trymon," he said, without turning, and noted with some
satisfaction the faint indrawing of breath behind him. "Good
of you to come. Shut the door, will you?"

[ The Light Fantastic, by Terry Pratchett ]

` Statue trap

Statue traps look like normal statues of a monster, until you try to walk on the same square as one. When you walk on the trap, it will transform the topmost statue on the trap into the monster it depicts. A statue trap can also be activated by searching, zapping force bolt, or applying a pick-axe. Technically, stone to flesh doesn't activate the trap, it just reanimates the statue if the monster was fleshy, otherwise it turns it in to a meatball. A stethoscope will give a revealing message to healers only, but will not activate the trap. Monsters will never set off these traps.[35]

Because of these traps it is a good idea to far look any statue you see. If the statue is of a monster you would rather not fight, don't step on it. If you have automatic searching don't even go near it. ("The statue comes to life! The mind flayer hits!")
However, you can throw another statue, preferably one of a weaker monster, onto the trap and then activate it. The new statue will come to life, leaving the old one inanimate. Zapping the trap with a wand of teleportation will teleport the statue without activating it. A wand of polymorph will not set it off either.

^ Teleportation trap

This teleports you to a random location on the map, unless it is a vault teleporter located in a closet behind ad aerarium, in which case you are teleported to the vault. Note that ad aerarium may also refer to a closet with a level teleporter, which will not put you inside a vault, so it is not wise to blindly walk into a closet without identifying the trap first.

Magic resistance will prevent you from being teleported. ("You feel a wrenching sensation.") If you want to use the teleporter (e. g. a vault teleporter) and you cannot teleport intrinsically, you may use ctrl + t to take the teleporter despite magic resistance. The vault's location will not be revealed if you have teleport control, so remove any source of teleport control if possible before stepping into the portal.

^ Trap door

A trap door is a hidden door located in the floor. When triggered the door falls open and creates a hole. It is identical to the simpler hole except that it starts out hidden. Just like with a hole, 2 or 3 levels is common, there is no upper limit, and you cannot fall beyond the Castle. Monsters never fall more than one floor.[38]

Generation: May be randomly generated at any dungeon level. Trap doors cannot be randomly generated on levels with non-diggable floors such as the Vibrating square level or the Castle, although the Castle contains several statically placed trap doors. If the floor is non-diggable, the trap door is replaced with a falling rock trap. Cannot be generated beneath a boulder. Unlike holes they are sometimes found in closets, with "Vlad was here" engraved in front of the door.

Encyclopedia entry

I knew my Erik too well to feel at all comfortable on jumping
into his house. I knew what he had made of a certain palace at
Mazenderan. From being the most honest building conceivable, he
soon turned it into a house of the very devil, where you could
not utter a word but it was overheard or repeated by an echo.
With his trap-doors the monster was responsible for endless
tragedies of all kinds.

[ The Phantom of the Opera, by Gaston Leroux ]

^ Vibrating square

Starting in 3.6.0, the vibrating square is counted as a trap, and thus detectible by methods that detect traps. This also prevents teleporting directly onto the vibrating square, so you'll need to pick a square next to it when using controlled teleports to reach it faster.

" Web

A spider web is a rare type of non-magical trap.

If you "stumble into a spider web", you will be unable to escape it for 0-12 turns, depending on your strength.

If your strength was high enough to escape in 0 turns, then "You tear through a web!" and the web is destroyed.

If you are wielding Sting, you always escape in 1 turn ("Sting cuts through the web!"), leaving the web intact.

This is the only trap to use the " symbol, rather than the ^ symbol. Attempting to untrap stuck monsters risks trapping you and spreading the web.

You can produce webs with the #monster command if you are a spider. All web-related messages are lovingly crafted to reflect whether things are happening to "your web" or "a spider web".

Generation: Never randomly generated above dungeon level 7[40]. For each web trap generated randomly, a giant spider is also generated[41]. Web traps are also generated for 3/4 (all, if you have the Amulet of Yendor) of giant spiders generated at level-generation time[42].

To remove: #untrap (difficult), walk in with greater than 18/50 strength, or burn it away with a wand of fire.
Note that if you fail to #untrap a monster or pet that is in the web, you will become stuck in a new web at your current position, in addition to the original web.
You can fill up the entire dungeon with webs in this way, if you so choose.

Encyclopedia entry

Oh what a tangled web we weave,
When first we practise to deceive!

[ Marmion, by Sir Walter Scott ]

Cold trap

This trap appears only in UnNetHack. In Sheol, it replaces fire traps. The amount of damages is the same, but the damage is cold damage instead of fire damage. They also have a small chance of appearing in a trap room.

Container traps

Containers can be searched with the #untrap command. A high luck can be helpful in avoiding the effects of container traps. Bad luck increases the likelihood of more dangerous traps. Be careful of trapped containers in shops, you will be charged for any items that are destroyed if you set off a trap that damages the merchandise. Container traps include:

Door traps

Trapped doors (and rarely, cursedtins) will explode when opened ("KABOOM!! The <object> was booby-trapped!"), causing damage, abusing strength and possibly constitution, and stunning you. The damage and duration of the stun depend on a number of factors, including (but not limited to) your level and how deep you have been in the dungeon.

Strategy

Avoiding traps in the dungeon takes patience and care. Therefore, the more time-consuming of these methods are only worthwhile when you are especially vulnerable. You can minimize your chances of stepping on a trap by paying close attention to monsters, pets, noises, and terrain. Be wary of the telltale signs of traps such as conspicuous boulders, suspicious corpses, or piles of rocks, darts or arrows. Traps that you've already discovered will also not be visible under items like these, so it's a good idea to use the trap id command if you need to step onto that square that looks suspicious, even though you may have already been in that area and discovered all traps. By walking only where you have seen pets or monsters safely walk, you can avoid most traps. Remember where you have safely stepped before. Elbereth can cause monsters to flee, possibly uncovering traps as they do. A leashed pet will whine if it is near a trap. Magic resistance and fire resistance can help nullify some of the more dangerous effects of traps.

The search command is a great way to uncover traps without setting them off. #Untrap can be used on doors and containers. You can improve your chances of finding traps if you: